Method and apparatus for detecting hot rail car surfaces

ABSTRACT

In one embodiment of the present invention, an apparatus for detecting a hot rail car surface comprises: an infrared sensor for acquiring an infrared signal from a rail car surface of a rail car and transducing the infrared signal into an electrical signal; a rank filter for filtering the electrical signal to produce a filtered array; a first peak detector for detecting a maximum filtered value of the filtered array; and a first comparator for comparing the maximum filtered value to a detection threshold to produce a filtered alarm signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation-in-part of U.S. application Ser. No.10/063,218, filed Mar. 29, 2002, now abandoned, which application isherein incorporated by reference.

BACKGROUND OF INVENTION

This invention relates generally to the field of detecting excessivelyhot rail car surfaces and more specifically to the use of rank filtersto process infrared signals emitted by rail car surfaces.

While the present disclosure emphasizes application of the presentinvention to detection of hot rail car wheel bearings, it will beobvious to one of ordinary skill in the art that the present inventionis equally applicable to the detection of other hot rail car surfacessuch as, by way of example but not limitation, rail car wheels.

Malfunctioning rail car wheel bearings radiate heat due to friction. Todetect such overheated bearings, in an attempt to warn the operator andstop the train prior to complete bearing failure and potential trainderailment, railroads have developed and deployed wayside hot bearingdetectors (HBDs). Typical HBDs utilize pyroelectric infrared sensors fordetecting heat profiles of the rail car wheel bearings as the rail carsroll past the sensor. As well as being pyroelectric, however, thesesensor devices may often also be piezoelectric; that is, electricaloutputs produced by these devices depend not only on the heat sensed,but also on sensed sound and vibration. The electrical noise pulsesinduced by undesirable piezoelectric effects are known as “microphonicartifacts”.

In some instances, microphonic artifacts present magnitudes similar tothose of hot bearings. As conventional HBDs rely mainly on signalmagnitudes for detection, microphonics and other phenomena can inducefalse alarms that result in stopping a train unnecessarily. Such falsestops cost the railroad significant time and money.

While the signal magnitudes of microphonic artifacts are comparable tothe signal magnitudes produced by truly hot bearings, the microphonicartifacts tend to present themselves as substantially sharper “spikes.”An opportunity exists, therefore, to reduce HBD sensitivity tomicrophonic artifacts through improved signal processing.

SUMMARY OF INVENTION

The opportunities described above are addressed, in one embodiment ofthe present invention, by an apparatus for detecting a hot rail carsurface comprising: an infrared sensor for acquiring an infrared signalfrom a rail car surface of a rail car and transducing the infraredsignal into an electrical signal; a rank filter for filtering theelectrical signal to produce a filtered array; a first peak detector fordetecting a maximum filtered value of the filtered array; and a firstcomparator for comparing the maximum filtered value to a detectionthreshold to produce a filtered alarm signal.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 illustrates a block diagram of an apparatus for detecting a hotrail car surface in accordance with one embodiment of the presentinvention; and

FIG. 2 illustrates filtered array and unfiltered array signals inaccordance with the embodiment illustrated in FIG. 1.

DETAILED DESCRIPTION

In accordance with one embodiment of the present invention, FIG. 1illustrates a block diagram of an apparatus 100 for detecting a hot railcar surface comprising an infrared sensor 110, a rank filter 140, afirst peak detector 150, and a first comparator 160. In operation,infrared sensor 110 acquires an infrared signal from a rail car surface120 of a rail car 130 and transduces the infrared signal into anelectrical signal 115. Rank filter 140 filters electrical signal 115 toproduce a filtered array 145.

The process of filtering using rank filter 140 comprises: incorporatinga new sample of electrical signal 115 into a data buffer; discarding theoldest sample in the data buffer; finding a rank value of the databuffer; and storing the rank value in filtered array 145. The length ofthe data buffer is referred to as the “filter length.” The “rank” of thefilter is a quantity between 0 and 1 and defines the fraction of thedata buffer containing values smaller than the rank value. For example,if the rank equals 0.5, then the rank filter finds the median value ofthe data buffer; if the rank equals 0.8, then the rank filter finds the80th percentile value (i.e., the smallest value greater than 80 percentof all the values); if the rank equals 0, then the rank filter finds theminimum value; and if the rank equals 1, then the rank filter finds themaximum value.

Filtered array 145 is passed to peak detector 150 wherein a maximumfiltered value 155 is detected, and first comparator 160 comparesmaximum filtered value 155 to a detection threshold 165 to produce afiltered alarm signal useful for alerting a train operator of anincipient failure of rail car surface 120.

Infrared sensor 110 comprises any electrical or electronic devicecapable of converting infrared electromagnetic radiation to electricalsignals; examples of infrared sensor 110 include, without limitation,photodiodes, phototransistors, photomultiplier tubes, and vidicon tubes.Rail car 130 comprises any vehicle capable of traveling on railroadtracks; examples of rail car 130 include, without limitation, box cars,ore cars, flat cars, tank cars, and locomotives. Rail car surface 120comprises any surface of rail car 130 visible from a wayside; examplesof rail car surface 120 include, without limitation, wheel bearingsurfaces and wheel surfaces. Rank filter 140, first peak detector 150,and first comparator 160 comprise any electrical or electronic devicescapable of performing the indicated operations; examples of rank filter140, first peak detector 150, and first comparator 160 include, withoutlimitation: analog electronic processors comprising, for example,operational amplifiers, sample and hold circuits, peak hold circuits,analog comparators, analog computation modules, and any combinationthereof; and digital electronic processors comprising, for example,single chip digital signal processors (DSPs), microprocessors,microcomputers, microcontrollers, small-, medium-, and large-scaleintegrated circuits, programmable logical arrays, programmable gatearrays, and any combination thereof.

In another embodiment in accordance with the embodiment illustrated inFIG. 1, apparatus 100 further comprises a wireless transceiver 170 and afilter parameter calculator 190. In operation, wireless transceiver 170acquires rail car surface characteristics transmitted by a wireless tag180 mounted on rail car 130. As a function of the rail car surfacecharacteristics, filter parameter calculator 190 calculates a filterlength and a rank of rank filter 140.

By incorporating knowledge of the particular rail car surface underobservation, better performance of rank filter 140 may be realized. Forexample, rank filter 140 passes signal pulses having widths longer thanthe product of the rank and the filter length; pulses narrower than theproduct of the rank and the filter length are rejected. A truly hotbearing produces a hot bearing signal pulse whose width is a function ofbearing geometry and of the known geometry of infrared sensor 110. Withknowledge of the bearing geometry, for example, communicated by wirelesstag 180, the expected width of the hot bearing signal pulse can becalculated, and the filter length and rank of rank filter 140 can betailored to pass the hot bearing signal pulse while rejecting narrowerpulses due to microphonic artifact.

Wireless transceiver 170 and wireless tag 180 comprise any devicescapable of wireless communication; examples of wireless transceiver 170and wireless tag 180 include, without limitation: electromagneticreceivers and transmitters operating at, for example, radio, infrared,or optical frequencies; commercially available receivers andtransmitters known as “Automatic Equipment Identification” (AEI); aswell as mechanical receivers and transmitters such as, for example,microphones and loudspeakers.

In still another embodiment in accordance with the embodimentillustrated in FIG. 1, apparatus 100 further comprises an unfilteredsignal buffer 200, a second peak detector 210, a second comparator 220,and an alarm comparator 230. In operation, unfiltered signal buffer 200buffers samples of electrical signal 115 to produce an unfiltered array205. Second peak detector 210 detects a maximum unfiltered value 215,which second comparator 220 compares to detection threshold 165 toproduce an unfiltered alarm signal. A censored false alarm signalresults when alarm comparator 230 compares the unfiltered alarm signalto the filtered alarm signal. A difference between the unfiltered alarmsignal and the filtered alarm signal indicates that rank filter 140 hassuccessfully prevented a false alarm. Knowledge that a false alarm wouldhave otherwise occurred can be used as an indicator that apparatus 100may be operating in a degraded mode.

In yet another embodiment in accordance with the embodiment illustratedin FIG. 1, the censored false alarm signal comprises a binary signalhaving a true value when the unfiltered alarm signal differs from thefiltered alarm signal and a false value otherwise, and apparatus 100further comprises a counter 240. Counter 240 counts the false values(i.e., the number of censored false alarms) to produce a censored alarmcount. While the existence of censored false alarms is indicative ofdegraded behavior, the censored false alarm count is further indicativeof the duration and severity of the degradation.

In again another embodiment in accordance with the embodimentillustrated in FIG. 1, apparatus 100 further comprises a failureisolator 250. Failure isolator 250 diagnoses a failure mode from thecensored false alarm count. By accumulating a censored false alarm counttime history, failure isolator 250 may employ statistical hypothesistesting techniques to identify (i.e., isolate) which among a group ofpreviously identified failure modes is most likely to have occurred.

Unfiltered signal buffer 200, second peak detector 210, secondcomparator 220, alarm comparator 230, counter 240, and failure isolator250 comprise any electrical or electronic devices capable of performingthe indicated operations; examples of unfiltered signal buffer 200,second peak detector 210, second comparator 220, alarm comparator 230,counter 240, and failure isolator 250 include, without limitation:analog electronic processors comprising, for example, operationalamplifiers, sample and hold circuits, peak hold circuits, analogcomparators, analog computation modules, and any combination thereof;and digital electronic processors comprising, for example, single chipdigital signal processors (DSPs), microprocessors, microcomputers,microcontrollers, small-, medium-, and large-scale integrated circuits,programmable logical arrays, programmable gate arrays, and anycombination thereof.

In accordance with the embodiment illustrated in FIG. 1, FIG. 2illustrates filtered array 145 and unfiltered array 205 as may begenerated during operation. Unfiltered array 205 suffers a microphonicartifact placing maximum unfiltered value 215 clearly above detectionthreshold 165. In contrast, the microphonic artifact has been removed infiltered array 145. Maximum filtered value 155 thus stays well belowdetection threshold 165, and a false alarm is avoided.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. An apparatus for detecting a hot rail car surface comprising: aninfrared sensor for acquiring an infrared signal from a rail car surfaceof a rail car and transducing said infrared signal into an electricalsignal; a rank filter for filtering said electrical signal to produce afiltered array; a first peak detector for detecting a maximum filteredvalue of said filtered array; and a first comparator for comparing saidmaximum filtered value to a detection threshold to produce a filteredalarm signal.
 2. The apparatus of claim 1 wherein said rank filter has arank of about one-half.
 3. The apparatus of claim 1 further comprising:a wireless transceiver for acquiring rail car surface characteristicsfrom a wireless tag mounted on said rail car; and a filter parametercalculator for calculating a filter length and rank of said rank filteras a function of said rail car surface characteristics.
 4. The apparatusof claim 1 further comprising: an unfiltered signal buffer for bufferingsaid electrical signal to produce an unfiltered array; a second peakdetector for detecting a maximum unfiltered value of said unfilteredarray; a second comparator for comparing said maximum unfiltered valueto said detection threshold to produce an unfiltered alarm signal; andan alarm comparator for comparing said unfiltered alarm signal to saidfiltered alarm signal to produce a censored false alarm signal.
 5. Theapparatus of claim 4 wherein: said censored false alarm signal comprisesa binary signal having a true value when said unfiltered alarm signaldiffers from said filtered alarm signal and a false value otherwise; andsaid apparatus further comprises a counter for counting said falsevalues to produce a censored false alarm count.
 6. The apparatus ofclaim 5 further comprising a failure isolator for diagnosing a failuremode from said censored false alarm count.
 7. An apparatus for detectinga hot rail car surface comprising: an infrared sensor for acquiring aninfrared signal from a rail car surface of a rail car and transducingsaid infrared signal into an electrical signal; a rank filter forfiltering said electrical signal to produce a filtered array; a firstpeak detector for detecting a maximum filtered value of said filteredarray; a first comparator for comparing said maximum filtered value to adetection threshold to produce a filtered alarm signal; a wirelesstransceiver for acquiring rail car surface characteristics from awireless tag mounted on said rail car; a filter parameter calculator forcalculating a filter length and rank of said rank filter as a functionof said rail car surface characteristics; an unfiltered signal bufferfor buffering said electrical signal to produce an unfiltered array; asecond peak detector for detecting a maximum unfiltered value of saidunfiltered array; a second comparator for comparing said maximumunfiltered value to said detection threshold to produce an unfilteredalarm signal; and an alarm comparator for conspiring said unfilteredalarm signal to said filtered alarm signal to produce a censored falsealarm signal.
 8. The apparatus of claim 7 wherein: said censored falsealarm signal comprises a binary signal having a true value when saidunfiltered alarm signal differs from said filtered alarm signal and afalse value otherwise; and said apparatus further comprises a counterfor counting said false values to produce a censored false alarm count.9. The apparatus of claim 8 further comprising a failure isolator fordiagnosing a failure mode from said censored false alarm count.
 10. Amethod for detecting hot rail car surfaces, the method comprising:acquiring an infrared signal from a rail car surface of a rail car;transducing said infrared signal into an electrical signal; filteringsaid electrical signal using a rank filter to produce a filtered array;detecting a maximum filtered value of said filtered array; and comparingsaid maximum filtered value to a detection threshold to produce afiltered alarm signal.
 11. The method of claim 10 wherein said rankfilter has a rank of about one-half.
 12. The method of claim 10 furthercomprising: acquiring rail car surface characteristics from a wirelesstag mounted on said rail car; and calculating a filter length and rankof said rank filter as a function of said rail car surfacecharacteristics.
 13. The method of claim 10 further comprising:buffering said electrical signal to produce an unfiltered array;detecting a maximum unfiltered value of said unfiltered array; comparingsaid maximum unfiltered value to said detection threshold to produce anunfiltered alarm signal; and comparing said unfiltered alarm signal tosaid filtered alarm signal to produce a censored false alarm signal. 14.The method of claim 13 wherein: said censored false alarm signalcomprises a binary signal having a true value when said unfiltered alarmsignal differs from said filtered alarm signal and a false valueotherwise; and said method further comprises counting said false valuesto produce a censored false alarm count.
 15. The method of claim 14further comprising diagnosing a failure mode from said censored falsealarm count.
 16. A method for detecting hot rail car surfaces, themethod comprising: acquiring an infrared signal from a rail car surfaceof a rail car; transducing said infrared signal into an electricalsignal; filtering said electrical signal using a rank filter to producea filtered array; detecting a maximum filtered value of said filteredarray; comparing said maximum filtered value to a detection threshold toproduce a filtered alarm signal; acquiring rail car surfacecharacteristics from a wireless tag mounted on said rail car;calculating a filter length and rank of said rank filter as a functionof said rail car surface characteristics; buffering said electricalsignal to produce an unfiltered array; detecting a maximum unfilteredvalue of said unfiltered array; comparing said maximum unfiltered valueto said detection threshold to produce an unfiltered alarm signal; andcomparing said unfiltered alarm signal to said filtered alarm signal toproduce a censored false alarm signal.
 17. The method of claim 16wherein: said censored false alarm signal comprises a binary signalhaving a true value when said unfiltered alarm signal differs from saidfiltered alarm signal and a false value otherwise; and said methodfurther comprises counting said false values to produce a censored falsealarm count.
 18. The method of claim 17 further comprising diagnosing afailure mode from said censored false alarm count.